package com.miemie;

import java.util.Scanner;
public class Test1 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()) {
            System.out.println(solver(scanner.nextInt()));
        }
    }

    public static int solver(int n) {
        int res = 0;
        for (int i = 1; i <= n; i++) {
            res += i;
        }
        return res;
    }
}
